1. Field of the Invention
This invention relates to the field of data processing. More particularly, this invention relates to data processing systems incorporating a cache memory.
2. Description of the Prior Art
It is known to provide data processing systems incorporating a cache memory for the purpose of increasing the speed of operation of the system by providing high speed access to a subset of the data and instructions words required by the system. Whilst cache memory offers high speed it is of a limited capacity and so careful selection and management of the information stored within the cache memory is required in order to gain the best from the system.
A part of proper cache control is the selection of which data should be held within the cache. It is known to provide cache control systems operating with various different replacement algorithms used to select a cache storage location to be overwritten with a new word when it is desired to place that new word into the cache following a cache miss. Examples of such selection techniques include least recently used, cyclic (i.e. sequential or "round robin"), or random. It is also known to provide cache memory systems in which some data words are locked in place within the cache and are not normally overwritten following a cache miss.